Re: Correct IDLE usage (was Reason for not allowing import twice but allowing reload())
On Thursday, March 3, 2016 at 9:38:11 AM UTC+5:30, Rustom Mody wrote: > On Thursday, March 3, 2016 at 8:11:20 AM UTC+5:30, Terry Reedy wrote: > > On 3/2/2016 10:22 AM, Rustom Mody wrote: > > > On Tuesday, March 1, 2016 at 12:23:02 PM UTC+5:30, Terry Reedy wrote: > > >> On 2/29/2016 7:42 AM, Rustom Mody wrote: > > >> > > >>> Is import needed at all when trying out in Idle? > > >> ... > > >>> So it does appear that > > >>> 1. import not necessary with(in) idle > > >>> 2. However import and f5 (ie is run as main) are different > > >>> > > >>> May some idle experts elaborate on this? Whats the idle idiom of > > >>> import-ing? > > >> > > >> Rustom, since I know that you are not a rank beginner, I have trouble > > >> understanding what you are asking. > > > > > > Heh! > > > I know some things; dont know many things > > > > > >> F5 when editing foo.py is equivalent > > >> to running "python -i foo.py" on a command line while 'in' the directory > > >> containing foo.py. In both cases, foo.py is run as a main module, with > > >> __name__ == '__main__'. The difference is that F5 runs foo.py under > > >> IDLE supervision, with results going into and interactive inputs coming > > >> from IDLE shell instead of the console interpreter. > > >> > > >> Imports are used in a module to access objects within the imported > > >> module. > > > > > > Let me try to explain again > > > > > > There is import and import. > > > There is the formal meaning of the import keyword in python -- call it > > > import-f > > > There is the informal expectation and need of programmers to 'pull > > > something > > > into python' -- call it import-i > > > > What do you mean by import-i that is different module import? Keyboard > > input with input()? File input with file.read(), etcetera? Running a > > file with 'python filename' or 'python -m filename'? > > I define something... either with > def foo()... > or > x = ... > > I want to see what foo does/what x is > I want to check that my understanding of these matches python's representation > of the same. > I could keep typing the the > def foo()... > but that can get painful quickly > > So I put these in a file... > And import! > > At this point I am pleased > Because what I expect of import (import-i) > and what python does with the import keyword (import-f) match... seemingly > > Until I go and change the def in the file and run the import again > Fails > Restart python -- works Just to be clear, I dont believe the problem is with import-f per se It is with overloading python to be both scripting engine and interactive interpreter. Both ruby and haskell find it expedient to separate the two Ruby has irb and ruby Haskell has ghc (compiler), runhaskell (scripting) ghci (interpreter) -- https://mail.python.org/mailman/listinfo/python-list
Re: Correct IDLE usage (was Reason for not allowing import twice but allowing reload())
On Thursday, March 3, 2016 at 8:11:20 AM UTC+5:30, Terry Reedy wrote: > On 3/2/2016 10:22 AM, Rustom Mody wrote: > > On Tuesday, March 1, 2016 at 12:23:02 PM UTC+5:30, Terry Reedy wrote: > >> On 2/29/2016 7:42 AM, Rustom Mody wrote: > >> > >>> Is import needed at all when trying out in Idle? > >> ... > >>> So it does appear that > >>> 1. import not necessary with(in) idle > >>> 2. However import and f5 (ie is run as main) are different > >>> > >>> May some idle experts elaborate on this? Whats the idle idiom of > >>> import-ing? > >> > >> Rustom, since I know that you are not a rank beginner, I have trouble > >> understanding what you are asking. > > > > Heh! > > I know some things; dont know many things > > > >> F5 when editing foo.py is equivalent > >> to running "python -i foo.py" on a command line while 'in' the directory > >> containing foo.py. In both cases, foo.py is run as a main module, with > >> __name__ == '__main__'. The difference is that F5 runs foo.py under > >> IDLE supervision, with results going into and interactive inputs coming > >> from IDLE shell instead of the console interpreter. > >> > >> Imports are used in a module to access objects within the imported module. > > > > Let me try to explain again > > > > There is import and import. > > There is the formal meaning of the import keyword in python -- call it > > import-f > > There is the informal expectation and need of programmers to 'pull something > > into python' -- call it import-i > > What do you mean by import-i that is different module import? Keyboard > input with input()? File input with file.read(), etcetera? Running a > file with 'python filename' or 'python -m filename'? I define something... either with def foo()... or x = ... I want to see what foo does/what x is I want to check that my understanding of these matches python's representation of the same. I could keep typing the the def foo()... but that can get painful quickly So I put these in a file... And import! At this point I am pleased Because what I expect of import (import-i) and what python does with the import keyword (import-f) match... seemingly Until I go and change the def in the file and run the import again Fails Restart python -- works > > > That there is some cognitive dissonance between import-f and import-i is > > seen > > in the OP's question itself; > > The OP's question is faulty. Repeat imports *are* allowed. > > > also Chris' "I dont believe the language should be changed" > > > > So the question is around: > > What is the best practice for doing import-i in python? > > Since I don't know what you mean by import-i, I cannot answer. > > > As the OP finds import-f works once and fails thereafter > > This is false. Import is a name binding statement. If a module is not > builtin, the first attempt to bind a name to a particular module has to > create the module and cache it in sys.modules. If it is builtin, the > first attempt caches the module. Subsequent attempts reuse the cached > module. Here are three imports that involve the same module. All three > run, none fail. > > >>> import itertools as it > >>> import itertools as it2 > >>> from itertools import count > >>> it, it2, count > (, , > ) > > If you want to create and cache a new module of the same name, perhaps > after editing a file, delete the cache entry before importing again. > Reload does this for you. What it does not attempt to do is to change or > delete all the old bindings and references. > > If one does plan to reload a module, then one should only access the > module *and its contents* via one name and keep track of any other > references to its contents, such as from instances to classes in the > module. This may be easy for a simple module of functions, but in the > general case, can be be difficult to impossible. > > > In idle one can get the desired result of import-i with F5 > > Is that right? > > Having no idea what import-i is, I cannot answer. I explained F5 in my > previous answer. > > > Also in general is there good usecases for import-f at that interpreter > > prompt > > As I said before, the purpose of an import is to access the contents of > module 2 from within module 1, where module1 can be the main module, > including in interactive mode. A beginner experimenting with core > python might proceed for hours without an import. Anyone experimenting > with a module must import the module first. I usually import one or > more modules in a given interactive session. > > > in idle? > > Whether the prompt is in a console text window or IDLE gui window is > irrelevant. The IDLE Shell gui window imitates interactive python in a > text console. It submits each statement entered to Python for execution > and displays the stdout and stderr results. > > > I think not but not sure of it > > Here is an example use of import for learning tkinter. > > >>> import tkinter as tk > > As expected, nothing
Re: Correct IDLE usage (was Reason for not allowing import twice but allowing reload())
On 3/2/2016 10:22 AM, Rustom Mody wrote: On Tuesday, March 1, 2016 at 12:23:02 PM UTC+5:30, Terry Reedy wrote: On 2/29/2016 7:42 AM, Rustom Mody wrote: Is import needed at all when trying out in Idle? ... So it does appear that 1. import not necessary with(in) idle 2. However import and f5 (ie is run as main) are different May some idle experts elaborate on this? Whats the idle idiom of import-ing? Rustom, since I know that you are not a rank beginner, I have trouble understanding what you are asking. Heh! I know some things; dont know many things F5 when editing foo.py is equivalent to running "python -i foo.py" on a command line while 'in' the directory containing foo.py. In both cases, foo.py is run as a main module, with __name__ == '__main__'. The difference is that F5 runs foo.py under IDLE supervision, with results going into and interactive inputs coming from IDLE shell instead of the console interpreter. Imports are used in a module to access objects within the imported module. Let me try to explain again There is import and import. There is the formal meaning of the import keyword in python -- call it import-f There is the informal expectation and need of programmers to 'pull something into python' -- call it import-i What do you mean by import-i that is different module import? Keyboard input with input()? File input with file.read(), etcetera? Running a file with 'python filename' or 'python -m filename'? That there is some cognitive dissonance between import-f and import-i is seen in the OP's question itself; The OP's question is faulty. Repeat imports *are* allowed. also Chris' "I dont believe the language should be changed" So the question is around: What is the best practice for doing import-i in python? Since I don't know what you mean by import-i, I cannot answer. As the OP finds import-f works once and fails thereafter This is false. Import is a name binding statement. If a module is not builtin, the first attempt to bind a name to a particular module has to create the module and cache it in sys.modules. If it is builtin, the first attempt caches the module. Subsequent attempts reuse the cached module. Here are three imports that involve the same module. All three run, none fail. >>> import itertools as it >>> import itertools as it2 >>> from itertools import count >>> it, it2, count (, , ) If you want to create and cache a new module of the same name, perhaps after editing a file, delete the cache entry before importing again. Reload does this for you. What it does not attempt to do is to change or delete all the old bindings and references. If one does plan to reload a module, then one should only access the module *and its contents* via one name and keep track of any other references to its contents, such as from instances to classes in the module. This may be easy for a simple module of functions, but in the general case, can be be difficult to impossible. In idle one can get the desired result of import-i with F5 Is that right? Having no idea what import-i is, I cannot answer. I explained F5 in my previous answer. Also in general is there good usecases for import-f at that interpreter prompt As I said before, the purpose of an import is to access the contents of module 2 from within module 1, where module1 can be the main module, including in interactive mode. A beginner experimenting with core python might proceed for hours without an import. Anyone experimenting with a module must import the module first. I usually import one or more modules in a given interactive session. > in idle? Whether the prompt is in a console text window or IDLE gui window is irrelevant. The IDLE Shell gui window imitates interactive python in a text console. It submits each statement entered to Python for execution and displays the stdout and stderr results. I think not but not sure of it Here is an example use of import for learning tkinter. >>> import tkinter as tk As expected, nothing visible happens. >>> root = tk.Tk() A default master windows is created *and displayed*. >>> b = tk.Button(root, text = 'hello world') Nothing visible happens. >>> b But an instance of the class was created. >>> b.grid() Button appears. Master window shrinks to fit. >>> t = tk.Toplevel(root) A new toplevel window appears. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
Re: Correct IDLE usage (was Reason for not allowing import twice but allowing reload())
On Tuesday, March 1, 2016 at 12:23:02 PM UTC+5:30, Terry Reedy wrote: > On 2/29/2016 7:42 AM, Rustom Mody wrote: > > > Is import needed at all when trying out in Idle? > ... > > So it does appear that > > 1. import not necessary with(in) idle > > 2. However import and f5 (ie is run as main) are different > > > > May some idle experts elaborate on this? Whats the idle idiom of import-ing? > > Rustom, since I know that you are not a rank beginner, I have trouble > understanding what you are asking. Heh! I know some things; dont know many things > F5 when editing foo.py is equivalent > to running "python -i foo.py" on a command line while 'in' the directory > containing foo.py. In both cases, foo.py is run as a main module, with > __name__ == '__main__'. The difference is that F5 runs foo.py under > IDLE supervision, with results going into and interactive inputs coming > from IDLE shell instead of the console interpreter. > > Imports are used in a module to access objects within the imported module. Let me try to explain again There is import and import. There is the formal meaning of the import keyword in python -- call it import-f There is the informal expectation and need of programmers to 'pull something into python' -- call it import-i That there is some cognitive dissonance between import-f and import-i is seen in the OP's question itself; also Chris' "I dont believe the language should be changed" So the question is around: What is the best practice for doing import-i in python? As the OP finds import-f works once and fails thereafter In idle one can get the desired result of import-i with F5 Is that right? Also in general is there good usecases for import-f at that interpreter prompt in idle? I think not but not sure of it -- https://mail.python.org/mailman/listinfo/python-list
Re: Correct IDLE usage (was Reason for not allowing import twice but allowing reload())
On 2/29/2016 7:42 AM, Rustom Mody wrote: Is import needed at all when trying out in Idle? ... So it does appear that 1. import not necessary with(in) idle 2. However import and f5 (ie is run as main) are different May some idle experts elaborate on this? Whats the idle idiom of import-ing? Rustom, since I know that you are not a rank beginner, I have trouble understanding what you are asking. F5 when editing foo.py is equivalent to running "python -i foo.py" on a command line while 'in' the directory containing foo.py. In both cases, foo.py is run as a main module, with __name__ == '__main__'. The difference is that F5 runs foo.py under IDLE supervision, with results going into and interactive inputs coming from IDLE shell instead of the console interpreter. Imports are used in a module to access objects within the imported module. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
